“There are swift- flowing rivers which dash through jagged cañons”
Doyle is describing a large area to the east of the Rockies. Interesting that he should use the Spanish word.

Much of the story concerns the Mormons. Brigham Young makes an appearance. One of the sentences Doyle puts into his mouth is, “We Elders have many heifers[1], but our children must also be provided.”
The footnote for [1] is:
“Heber C. Kemball, in one of his sermons alludes to his hundred wives under this endearing epithet.”
I would also mention that, in my dialect at least, it would be normal to say “our children must also be provided for”, rather than “provided”, in such a sentence.

From: The proverbs Epigrams and Miscellanies of John Heywood, edited by John S. Farmer, London, 1906, in The first Hundred of Epigrams Invented and Made by John Heywood, Londini, 1592, p. 142 [Farmer] [link here]:

Etymology: Found first in the comb. beetle-browed (1362); much later (1532), beetle is treated as a separate word in beetle brow(s ; whence a derived verb to beetle v.1 (see beetle n.1) formed by Shakespeare.
(As the 14–15th cent. form had bitel- , bytel- , it has been proposed to identify it with bitel adj. ‘biting, cutting like a sharp-edged tool,’ used by Ormin and Layamon, which is phonetically possible: but, beside the hardly satisfactory sense, there is the difficulty that bitel appears to have been obsolete for 160 years when the first example of bitel-brouwed occurs. It is more likely that the word here is one of the two ns. beetle n.1, both extant in 14th cent., and both having the form bitel. The choice depends largely upon the exact meaning originally attached to ‘beetle-browed,’ which was a reproachful epithet, and appears to have referred to the shaggy prominence of the eye-brows. (Brow in Middle English was always = eyebrow, not = forehead.) It is probable therefore (as suggested by Dr. F. Chance) that the comparison is to the short tufted antennæ of some species of beetles, projecting at right angles to the head, which may have been called ‘eyebrows’ in English as well as in French; for in French the expression sourcils de hanneton ‘cockchafers’ eyebrows’ is the name given to a species of fringe made in imitation of the antennæ of these insects.)

A type of mallet has been called a beetle from the ninth century to date.

The origin of “beetle” (the insect) is apparently from the Old English verb bitul/ol and bitan, meaning bite.

I was not previously familiar with this usage of “tetanus”, meaning extreme muscular contraction generally: I would have taken tetanus to be specifically a condition caused by C. tetani. Apparently the usage above is still in use.

In modern American medical English, at least, the more usual term for extreme uncontrollable muscular contraction not caused by Clostridium tetani would be “tetany” or “tetanic contraction”. This sense of “tetanus” is still listed in medical dictionaries but I think it’s pretty much obsolete, due to the danger of confusion (treatment for drug-induced or hypocalcemic tetany and clostridial tetanus being rather different).